Capacitance shorting switch for electrical translating devices



1964 R. s. BOWSER ETAL 3,161,733

CAPACITANCE SHORTING SWITCH FOR ELECTRICAL TRANSLATING DEVICES Filed Nov. 1. 1961 ROBERT S. BOW ER RICHARD C. HUGEINS I VEN TOR 3 TTOR Y United States Patent 3,161,733 CAPACITANCE SHORTING SWITCH FOR ELECTRICAL TRANSLATING DEVICES Robert S. Bowser, Wakefield, and Richard C. Huggins,

Somerville, Mass, assignors to Sylvania Electric Products Inc., a corporation of Delaware Filed Nov. 1, 1961, Ser. No. 149,390 3 Claims. (Cl. 200-16) This invention relates to electrical switches and circuits, and more particularly to electrical apparatus for preventing capacitive effects in a group of associated electrical translating devices having a common connection.

Capacitive coupling can arise when a group of unshielded wires or conductors are placed in close or abutting relationship in a common cable, especially if the conductors are connected through a switch from one side of a power line to a group of devices having a common connection to the other side of the power line. Under such conditions, if the switch to one of the conductors is closed, the device connected to that conductor will operate, but if the capacitive coupling through the cable to another device is of low enough impedance, the latter device will also operate. Such an effect is generally undesirable.

Nevertheless, it is often necessary to use unshielded conductors in cable, for electrical connection from a power source to a group of electrical devices, for reasons of size and relative economy. According to our invention, however, we have discovered that the undesirable aspects of capacitive coupling can be eliminated by short circuiting the devices to which the line switch is not closed, the short circuit being placed across both the device and the cable leading to it on the open side of the switch. In that way, only those devices conductively connected to both sides of the line will operate.

Although there are many examples of electrical devices which may be associated with our switch, we have found that our invention is particularly useful when used in conjunction with a segmented electroluminescent device, that is an electroluminescent device which is divided into a multiplicity of individually operable units positioned on a common base plate which serves as a common potential source in the circuit.

For example, an electroluminescent device which may be associated with our switch is described in the United States Patent to Edmonds No. 2,773,216. In that patent, the segments of the lamp may be formed to define a number of segmented areas or units, each of which is electrically insulated from the other by sand blasting a light transmitting, electrically conductive coating which has been provided on the surface of the device. The desired size and shape of these various segments is not important to the present invention and thus, they may be varied at will for different applications.

In one embodiment of the invention, each of the segments of the electroluminescent device are connected to the switch by separate conductors, the main body of the number of segmented units in the electroluminescent device. The segmented units are individually connected to their respective spring-leaf contacts by separate unshielded conductors that pass through a common cable. The free ends of the spring-leaf contacts normally rest upon indi- 3,161,733 Patented Dec. 15, 1964 device and thence back to the negative potential of the circuit.

Beneath the spring-leaf contacts, a guideway provided in the insulated base member, and a conductive plunger, mating with the shape of the guideway is slidably arranged therein. A main conductive strip connected to the power source is fixed at the entrance to the guideway and is placed in electrical contact with the conductive plunger. On the end of the conductive plunger we provide an insulated, tapered cam nose which sequentially lifts the spring contacts from engagement with their respective mating ground points to avoid a short circuit. Once the spring contact has been lifted, the current may be passed from the conductive plunger to the individual spring contacts. With deeper penetration of the plunger into the guideway, the cam nose will sequentially lift one springleaf contact after another and thus energize various segments of the electroluminescent device. The above described arrangement is quite useful for devices such as an electroluminescent speedometer or an electroluminescent level indicating device. To decrease the size this switch can be designed in more compact assemblies for example it may be round.

The primary object of this invention is the elimination of capacitance coupling in electrical translating devices connected to line switches through a cable of unshielded conductors in proximity to each other.

A feature of this invention is a switch for selecting the devices which are to operate, the switch normally short circuiting all the devices connected to it, but removing the short circuit on a particular device as the line is connected to that device, and preferably just before the line is connected.

Another feature of this invention is to provide a switching arrangement whereby a capacitive coupling build-up in a cable of unshielded wires can be relieved by routing the leakage energy through a controlled path.

And an advantage of this invention is that positive control over separatesegments of on electrical translating device is afforded and leakage from capacitive coupling is eliminated.

Other objects, features and advantages of the invention will be apparent from the following specification, taken in connection with the accompanying drawings in which:

FIG. 1 is a schematic arrangement showing the main components of this invention and their electrical connection to each other.

FIG. 2 is an enlarged cross-sectional view of the switch base member taken on the line 2-2 of FIG. 1.

The main components of this invention are viewed in FIG. 1 wherein an electroluminescent device .1 is used as an indicator source. The device normally is constructed with conductive coating which covers the entire face, but for this particular applicationwe have sandblasted certain portions of the top conductive surface to define a number of segmented conductive areas 3 electrically insulated from each other. Each of the segmented units Shave separate conductors 5 leading thereto.

An electrical switch 7 having a main rectangular insulating body 9 is used with a series of equally spaced spring-leaf contacts 11 fixed on the top surface thereof by conductive pins 13. The free ends of each of the spring-leaf contacts 11 rests upon a mating ground contact 15. The number of spring leaf contacts 11' can be identical to the number of segmented units 3. Beneath, and running perpendicular to the spring-leaf contacts 11,

, a guideway 17 is journaled the full length of the'insulated vidual ground contacts and the ground contacts are in turn connected to a common ground strip secured to insulating base member.

The ground strip connectedby a conductor to the ground portion of the electroluminescent 7 body 9.

' At the gateway of the guideway 17, a conductive strip gated conductive plunger 21 generally equal in width to the guideway 17, but extending above the top thereof, is provided for conducting current from the conductive strip 19 to each member of the series of electrical contacts 11. The plunger 21 has at its foremost tip, an insulated camming nose 23 and at its opposite end the plunger has an insulated handle 25. The plunger 21 is adapted to travel in the guideway 17 of the switch 7. We have shown the plunger 21 as a manually operated implement for convenience, but it may also be operated by various other means such as a motor from a speedometer or other such devices. Such power operation would be further simplified by using a circular switch.

A suitable power source 31 is used to provide current for the circuit and one lead which may be the positive potential is directly connected to the conductive strip 19 by the conductor 33. As mentioned above, the springleaf contacts 11 are individually connected to their respective segmented units 3 of the lamp 1 by conductor 5.

The conductors 5 are connected to the lamp from the spring-leaf contacts 11 through a multi-strand cable 37 and the segmented units 3 are directly connected to the negative potential of the power source 31 by conductor 41 to complete the circuit of the lamp.

A by-pass circuit is provided from the ground points 15 which are connected to a common ground 43 positioned on the side of the insulated base member 9. A conductor 45 connects the ground strip 43 to the ground base of lamp 1 and thence to the negative side of the circuit.

With the above described circuitry, the plunger 21 will be moved into the guideway 17. At the outset of the movement of the plunger 21 the insulated cam tip 23 of the plunger will contact and lift the first spring-leaf contact 11 from its ground point 15, see FIG. 2. Also the conductive plunger 21 will bear against the conductive strip 19, which is positioned at the gateway to the guideway 17, to energize the shaft portion. With further travel of the plunger into the guideway, the conductive portion of the plunger 21 will con-tact the first'raised spring-leaf contact 11, thereby completing a circuit to the lamp over conductor 5 and thence back to the negative side of the power source 31 over the conductor 41;

As mentioned above the conductors 5 are unshielded and are funneled through the multi-strand cable 37 to connect the switch 7 to the lamp 1. Although capacitance coupling would normally be present in the cable under these conditions, according to our invention, the undesirable operation of the other segments of the electroluminescent device does not appear.

It is apparent that changes and modifications may be made within thespiritand scope of the instant'invention, but it is our intention only to be limited by'the scope of the following claims.

As our invention we claim:

1. An electrical switch in combination with a plurality of unshielded wires in a cable, each leading to separate portions of a segmented electrical translating device, said switch comprising: an insulated base member; a series of spring-leaf contacts positioned on said base member; a common ground strip on said base member connected to said electrical translating device, each of said springleaf contacts when closed being electrically connected to said common ground strip; a guideway in said insulated base member beneath said spring-leaf contacts; means within said guideway for opening said spring-leaf contacts and for conducting current sequentially to each of said spring-leaf contacts and thence to said electrical translating device.

2. An electrical switch in combination with a plurality of unshielded wires in a cable each leading to separate portions of a segmented electrical translating device, said switch comprising: an insulated base member; a series of spring-leaf contacts positioned on said base member and spring biased against a series of individual ground points, each of said spring-leaf contacts being disposed upon said base member; a common ground strip on said base member connected to said electrical translating device and said ground points, each of said spring-leaf contacts when closed being electrically connected to said common ground strip by way of the said individual ground points, a guideway in said insulating base member beneath said spring-leaf con-tacts; means within said guideway for biasing said spring-leaf contacts from their respective ground points and current supplied sequentially to each of said spring-leaf contacts and thence to said electrical translating device.

3. An electrical switch in combination with cabling of unshielded wires leading to a segmented electrical translating device comprising: an insulating base member; a series of spring-leaf contacts on said insulating base member, said spring-leaf contacts spring urged to contact a common ground; a guideway positioned beneath said spring-leaf contacts, current input means connected to a power source, said current input means being positioned at the entrance to said guideway and electrically associated with a conductor plunger slidably positioned within said guideway and adjacent the first of said spring-leaf contacts, an insulated camming tip on the anterior portion of-said conductive plunger, said insulating camming tip adapted to elevate in succession said spring-leaf contacts from their ground points when said plunger is inserted into said guideway; conductive'portion of said plunger being disposed so thatupon contact with said first springleaf contact said plunger will conduct current thereto, and upon further movement of said plunger into said guide way said plunger will contact other elevated spring-leaf contacts in succession, thus passing current thereto and thence to the respective segmented portions of said elevated translating device over unshielded wires conveyed by said cable and wherebyunelevated spring-leaf contacts will provide a by-pass circuit to eliminate capacitance coupling generated in said cable of unshielded wires.

, I References Cited by the Examiner UNITED STATES PATENTS 1,693,173 11/28 Brown 200l53 2,199,477 5/40 Besag 200153 2,528,345 10/50 De Champs 20011 2,773,216 12/56 Edmonds 3l5-169 3,024,334 3/62 Rhodes 200-l1 3,030,461 4/62 Gantz 200--153 BERNARD A. GILHEANY, Primary Examiner. 

1. AN ELECTRICAL SWITCH IN COMBINATION WITH A PLURALITY OF UNSHIELDED WIRES IN A CABLE, EACH LEADING TO SEPARATE PORTIONS OF A SEGMENTED ELECTRICAL TRANSLATING DEVICE, SAID SWITCH COMPRISING: AN INSULATED BASE MEMBER; A SERIES OF SPRING-LEAF CONTACTS POSITIONED ON SAID BASE MEMBER; A COMMON GROUND STRIP ON SAID BASE MEMBER CONNECTED TO SAID ELECTRICAL TRANSLATING DEVICE, EACH OF SAID SPRINGLEAF CONTACTS WHEN CLOSED BEING ELECTRICALLY CONNECTED TO SAID COMMON GROUND STRIP; A GUIDEWAY IN SAID INSULATED BASE MEMBER BENEATH SAID SPRING-LEAF CONTACTS; MEANS WITHIN SAID GUIDEWAY FOR OPENING SAID SPRING-LEAF CONTACTS AND FOR CONDUCTING CURRENT SEQUENTIALLY TO EACH OF SAID SPRING-LEAF CONTACTS AND THENCE TO SAID ELECTRICAL TRANSLATING DEVICE. 